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15.5
Usage Notes
15.5.1
Notes on Register Access
TCNT and TCSR differ from other registers in being more difficult to write to. The procedures for
writing to and reading from these registers are given below.
(1) Writing to TCNT and TCSR
These registers must be written to by a word transfer instruction. They cannot be written to by a
byte transfer instruction.
TCNT and TCSR both have the same write address. Therefore, satisfy the relative condition
shown in figure 15.6 to write to TCNT or TCSR. To write to TCNT, the upper bytes must contain
the value H'5A and the lower bytes must contain the write data before the transfer instruction
execution. To write to TCSR, the upper bytes must contain the value H'A5 and the lower bytes
must contain the write data before the transfer instruction execution.
<TCNT write>
Address : H'FFBC
<TCSR write>
Address : H'FFBC
(2) Reading from TCNT and TCSR
These registers are read in the same way as other registers. The read address is H'FFBC for TCSR
and H'FFBD for TCNT.
15
15
Figure 15.6 Writing to TCNT and TCSR
8 7
H'5A
8 7
H'A5
Rev. 1.00, 09/03, page 423 of 704
0
Write data
0
Write data
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